In wind turbine applications there is a trend to build increasingly higher towers in order to obtain increased power. Increased height results in higher loads at the base of the tower. Therefore, the lower sections of the tower must be made wider. The diameter at the bottom of wind turbine towers is increasingly larger to the point of not being able to be transported by road easily. At this point, two alternatives have been proposed consisting in either making the lower portion of the tower in situ (e.g. of concrete) or making the tower using prefabricated elements which are then assembled in situ.
As used herein, a tower section includes of two or more shell segments such that, in an assembled condition, the shell segments define a tower section. Each tower section is thus a substantially hollow structure corresponding to a level in the wind turbine tower. Tower sections are formed through the use of e.g. connecting means for mutually joining two adjacent shell segments along a substantially vertical joint.
Methods for assembling shell segments are known in the art. For example, WO2010067166A1 discloses a method for building a wind turbine tower in which pre-assembled concrete segments of a tower section are provided. Segments are then lifted and positioned to obtain a full tower section. The method disclosed in this document makes use of a number of connecting elements such as pre-stressing tendons, cables or strands that are fitted within ducts in cylindrical modules, which makes the resulting assembly process complex and capital intensive.
Another example is WO2010049313A2 that discloses a method for erecting a segmented steel tower for a wind turbine in which a climber is first built, carrying the top section of the tower. The climber carries the weight of the top section during all the installation of the segments of the tower, but is independent of the weight of the segmented tower. The method disclosed in this document requires two supporting structures, one of them with attaching lifting mechanism, which requires high-resistance capacities and makes more complex and expensive the assembly process.